When you start looking for a design firm to work with, you probably have a project or two in mind for them to take on. Maybe you’re looking for a fresh website design, or perhaps you’d like your existing site to be refreshed or redesigned. These all seem like simple tasks for any experienced design firm to handle — but what other services do these firms offer?

The best design firms in the world can do more than make your website look great. They can also improve its functionality, use SEO to get it ranking better, and increase metrics important to your business.

Here’s a quick look at the kinds of services the agencies at the top of our list offer.

Website Design

This one is a given! Reputable design agencies can create beautiful, mobile-friendly, and modern websites that match your brand’s styling and meet your needs. They can help you with the process from start to finish, creating wireframes, mockups, and eventually a finished and fully functional site.

Note that website design doesn’t just involve making a site look good. Design firms also have to create the “backend” of a new site, too, which involves selecting a content management system (or CMS), doing custom development, and adding your information or products so they display properly to website visitors.

Website Redesign

Design agencies also offer website redesign services for those who need their existing site updated or completely made over. Depending on what level of design or functionality is needed, a redesign may be a short process done with the same CMS, or it may require a new CMS to be used instead.

Design firms should also be able to assist with website “refreshes.” Website refreshes are a growing trend in which sites change different graphical elements over time, but keep the “core” site design the same. Refreshes may also go hand-in-hand with A/B testing, which we’ll cover next.

A/B and CRO Testing

Sometimes it’s difficult to know what design elements will appeal the most to website visitors. Or you may want to test different calls to action, button colors, or even entire landing pages. The best design agencies will be able to help you with either A/B or conversion rate optimization (CRO) testing.

A/B testing is a test in which different elements of a website are displayed to different groups of users. For example, version A of a website may be shown to 50% of visitors, and version B to the other 50%, to measure which version drove the most conversions or clicks. If version A has more of the desired interaction, that is the one that will be permanently implemented.

CRO testing goes hand-in-hand with this. This kind of A/B testing aims to increase conversions on a website, whether that means increasing the number of forms filled out or driving up purchase rates in an ecommerce store. Your agency should be able and even excited to test these elements for you.

Custom Development

Not every site is the same. Some agencies may offer “cookie cutter” website design and development solutions, and this may be fine for you. But if you need integration with custom software or services, or special functionality on your website, your firm will need to provide these custom development services for you.

Search Engine Optimization (SEO)

As we’ve already said, it isn’t necessarily enough for your website to look good. A beautiful website is meaningless if it doesn’t get found in search. That’s why the best firms offer search engine optimization, or SEO, services to their clients.

SEO consists of many activities and methods designed to increase your ranking in search engines like Google, Bing, and Yahoo. It can include simple tasks like website copywriting, or more complex ones like targeted outreach and link building. Your agency should be able to help you with SEO to ensure your beautiful new site is seen by as many people as possible.

Ongoing Website Maintenance

Finally, you should seek out firms that offer ongoing website maintenance plans. A new site isn’t something you can simply “set and forget” — it will need ongoing design updates and functionality additions to stay current and displaying properly on all devices.

The best firms will quote you not only the price for a new website design, but also an ongoing maintenance package that covers new requests, maintenance tickets, or bug fixes.

These are the kinds of services that reputable design agencies should offer. Agencies may offer services and options far beyond these — each firm is different. Carefully review each firm’s packages and plans before choosing them to ensure that they are able and willing to meet your individual needs.

Not sure where to find reputable agencies to evaluate for your design and development needs? Try our list of the top agencies for 2014 to get started!